xx. CRA YFISHES. 289 



spicuous in front are the long feelers, close to which are 

 the smaller feelerets. Near the middle line in front the 

 shell ends in a pointed projection, called the rostrum. 

 This is worth examining carefully, so beautifully is it 

 fashioned. On either side of it are two sharp flattened 

 plates, which are movable, and are connected with the 

 feelers. And just above them are the eyes, which are 

 carried on short movable stalks. It is a curious and 

 interesting fact that the crayfish in the Mammoth Cave 

 in Kentucky, where all is darker than darkest night, are 

 blind. Of what use would eyes be to them ? But they 

 still retain the stalk upon which the eyes are situated in 

 their more fortunate relations outside the cave. 



I wonder whether you could find the crayfish's ears ! 

 I expect not. They are to be found on the lowest and 

 largest joint of the feeleret, one on each side. In this 

 joint there is a little slit guarded with hairs, which leads 

 into the hollow of the ear. Organs of hearing are some- 

 times found in strange places. Thus, the grasshopper has 

 them in his legs ; and the brine-shrimp, mysis, a distant 

 relation of the crayfish, has them in his tail. 



All the front part of the body, as far back as the hinder 

 pair of legs, is encased in a continuous piece of shell 

 armour, which protects the back and sides. It is this 

 shell-armour which gives to the group of organisms to 

 which the crayfish belongs the name of crustaceans. The 

 hinder part of the body, that which is popularly called the 

 tail, is encased in a series of overlapping plates of shell- 

 armour, so that this part is freely movable, and can be 

 either straightened out or bent in under the body. But it 

 cannot be moved from side to side. The crayfish can tuck 

 his tail under his legs when he is frightened, but cannot 

 wag it when he is pleased. The tail ends in a flattened 

 plate fringed with long hairs at the back, and on either 



U 



